Notes on reason and logical fallacies

Reason:  a structured, systematic thought process used to arrive at a valid conclusion.

Empiricism:  The epistemological belief which claims that all knowledge, and ultimately superior knowledge, originates from the 5 senses.  Empiricists would challenge the rationalists and claim that reason and logic were too linear and predictable, and humans aren’t very good at reasoning anyway.

Rationalism: The epistemological belief which claims that reason, which allows us to transcend our senses, is the superior source of knowledge.  Rationalists would challenge the empiricists and claim that we cannot always trust the knowledge we get from our senses, and that reason alone can provide knowledge that is more certain and reliable.  

Types of Knowledge:

Propositional vs Procedural

• Propositional knowledge:      Knowledge OF           Knowledge THAT

  • Can be expressed in propositions, or declarative statements of fact.  

  • Academic education is mostly propositional.

    • I know THAT Davy Crockett died in the battle of the Alamo.

• Procedural knowledge:  Knowledge HOW

  • Knowledge gained through experience.  CAS is mostly procedural knowledge. 

  • Skills that can be used and applied

    • I know HOW to change a flat tire.  

A priori and a posteriori refer to two different types of knowledge, or alternatively to two different ways in which beliefs can be justified. A priori knowledge acquires its justification prior to, or independently of, any observational or empirical evidence (e.g. scientific evidence, simply looking and observing something in the world, etc). A posteriori knowledge, by contrast, is justified only after, or as a result of, observational or empirical evidence. Mathematical truths, truths by definition, and logical deductions from other a priori knowledge are commonly cited examples of beliefs that can be justified a priori, without empirical evidence. Most other types of belief, including personal experiences, historical knowledge, scientific knowledge, etc, are justified a posteriori, through appeal to empirical evidence of some sort.

1. A Priori

A priori and a posteriori are two of the original terms in epistemology. A priori literally means “from before” or “from earlier.” This is because a priori knowledge depends upon what a person can derive from the world before even the need to directly experience it. This is better known as reasoning. Of course, a degree of experience is necessary upon which a priori knowledge can take shape.

Let’s look at an example. If you were in a closed room with no windows and someone asked you what the weather was like, you would not be able to answer them with any degree of truth. If you did, then you certainly would not be in possession of a priori knowledge. It would simply be impossible to use reasoning to produce a knowledgeable answer.

On the other hand, if there were a chalkboard in the room and someone wrote the equation 4 + 6 = ? on the board, then you could find the answer without physically finding four objects and adding six more objects to them and then counting them. You would know the answer is 10 without needing real world experience to understand it. In fact, mathematical equations are one of the most popular examples of a priori knowledge. 

2. A Posteriori

Naturally, then, a posteriori literally means “from what comes later” or “from what comes after.” This is a reference to experience and using a different kind of reasoning (inductive) to gain knowledge. This kind of knowledge is gained by first having an experience (and the important idea in philosophy is that it is acquired through the five senses) and then using logic and reflection to derive understanding from it. In philosophy, this term is sometimes used interchangeably with empirical knowledge, which is knowledge based on observation.

It is believed that a priori knowledge is more reliable than a posteriori knowledge. This might seem counter-intuitive, since in the former case someone can just sit inside of a room and base their knowledge on factual evidence while in the latter case someone is having real experiences in the world. But the problem lies in this very fact: everyone’s experiences are subjective and open to interpretation. A mathematical equation, on the other hand, seems to be an undeniable truth.

Deductive and Inductive Reasoning

deductive reasoning:  (deductive=decrease)  (general to specific) 

• Starts with a general rule, a premise, which we accept as true. Then from that rule, we make a valid conclusion about something more specific.  

  • All men are mortal.  

  • Socrates was a man.  

  • Therefore, Socrates was mortal.  

• Deductive conclusions must be valid if the premises are also valid.  Deductive conclusions are the most certain, although the knowledge is not always very insightful.  

inductive reasoning:  (inductive=increase)  (specific to general)  

• draws a general conclusion or theory based on multiple, specific observations or experiments.  

  • crime solving is inductive   

  • When we use the past to predict the future, we are using induction.  

• Induction is not always reliable!   

• Every swan I have ever seen is white, so therefore all swans are white.   

Logical Fallacies

A logical fallacy is an error in thinking.  They can be intentional or accidental.  There are many fallacies, but we will focus on the 10 described below.   Some logical fallacies go by multiple names.  

SLIPPERY SLOPE

• This is a conclusion based on the premise that if A happens, then eventually so will B, then, C, and so on, leading toward an undesirable but usually unlikely result.  The argument mistakenly tries to equate “A” with something else.
  
  

If the government decides to ban SUVs because they pollute the environment, eventually they could ban all vehicles. 

If the government starts restricting our gun rights, eventually we won’t have guns at all. 

HASTY GENERALIZATION

This is a conclusion based on insufficient or biased evidence. In other words, you are rushing to a conclusion before you have all the relevant facts.

• ”Even after the first 10 minutes, I can tell this is a terrible movie.”

• This person is making a premature judgment based on limited information.

POST HOC ERGO PROPTER HOC (FALSE CAUSALITY)  

• This assumes that “A” must have caused “B” since “B” happened right after “A”. 

“I drank bottled water last period, and now I am sick, so the water must have made me sick.”

• In this example, the author assumes that if one event chronologically follows another the first event must have caused the second.  While it is possible, it’s not certain.
  
  
  

FALSE DILEMMA

• This is a conclusion that oversimplifies the argument by reducing it to only two sides or choices.

We can either stop using cars which pollute the air, or we will destroy the earth.

• In this example, the two choices are presented as the only options, yet the author ignores a range of choices in between.  By doing this, we can be cornered into making a choice that may benefit somebody else.
  
  

AD HOMINEM

• This is an attack on the character of a person rather than the argument.

“My opponent has been married 5 times!  Can we trust him with the budget?”

• The person’s marital history may have little to do with how that person will perform his or her job.
  
  

RED HERRING

• This is any diversionary tactic that avoids the real argument with some sort of distraction. 

 
Example:  The level of mercury in our seafood may be unsafe, but what will fishers do to support their families?

• In this example, the author switches the discussion away from the safety of the food and talks instead about an economic issue, the livelihood of those catching fish.
  
  

STRAW MAN

• This move misrepresents an opponent's viewpoint, usually through oversimplification or exaggeration, and then attacks that distorted argument instead.

Example: “Our school principal just wants to limit our freedoms and ban everything that’s fun!” 

• The reasons behind school rules are much more complicated than this, and we are making assumptions about the principal’s motivations.  

AD IGNORANTIUM

• Claiming that something is true based on the grounds that there is no evidence to disprove it.  

Example:  “There is no evidence available to disprove that Mr. Green is a communist spy, so he must be one.”

• Positive evidence is required for proof. 
  
  
  

FALSE ANALOGY

• This is comparing two things which may seem similar on the surface but are actually different in an important way.  

“Based on graduation rates, private schools do a much better job at educating students than public schools.”  

• This comparison fails to recognize that the situation is much more complex;  private and public schools are funded differently, and private schools do not have to accept all students like public schools do.  

APPEAL TO AUTHORITY

• This assumes that any claim coming from an authority or expert must be true.  

The world’s top economist claims that we are headed for a recession, so it must be true.

Dr. Fauci says that the Covid vaccine will prevent the transmission of covid, so I’m going to get the vaccine. 

• Although we should respect the knowledge and experience of our experts and authorities, they are not infallible.  

Below are some of the questions we discussed as a class when we began our unit on reason:

1. In what kinds of problems or situations would reason be particularly helpful and useful?   What games involve logical reasoning?  

2. In what kinds of problems or circumstances would reason not be very helpful?  

3. Which of your classes seems to rely most upon reason for the knowledge it has accumulated? Explain.  Which of your classes don’t seem to rely much on reason for its knowledge?    

4. Is there anything that might interfere with our ability to reason?  Explain.

5. Do animals display reason?  If you were to devise an experiment that would measure an animal's ability to reason, what would it be?

6. What does it mean to be irrational?  Are emotions irrational?  What about religious faith?

7. How useful is logic and reason for making  moral decisions?  Explain. 

8. How can reason allow us to go beyond the immediate evidence of our senses?  Explain